In heating systems comprising a combustion air blower and a fuel valve for providing fuel to a burner, it is generally desired to provide fuel to the burner only when proper conditions exist for flame and to maintain an optimum fuel-to-air ratio when the burner is in operation. Prior art approaches to these problems are relatively complex. Accordingly, the present fuel gas controls were developed.
Systems incorporating the present invention are typically simplified over prior art systems and may incorporate one or more of three separate and distinct features: (1) the present invention may be incorporated to allow fuel to flow only upon sensing a predetermined minimum air flow; (2) the present invention may be incorporated to modulate the fuel flow so that a fixed fuel-to-air ratio is maintained; and (3) the present invention may be incorporated to shut off fuel completely if air flow substantially ceases, such as in the case of a blocked stack or malfunctioning combustion blower. While some or all of these features are available in prior art systems, these prior art systems are far more complex than systems incorporating the present invention.
Examples of systems over which the present invention provides simplification include those disclosed in U.S. Pat. No. 4,251,025. In those systems, for example, a separate pressure switch is required to check for a blocked stack, and this pressure switch is incorporated with a specialized control system which shuts off the fuel flow if pressure conditions are not correct. Through the present invention, no pressure switch or specialized control system for shutting off the valve is required.
The fuel gas control disclosed in U.S. Pat. No. 4,251,025 is typical of the relatively complex prior art controls which incorporate some or all of the three features listed above. Such prior art controls require a regulator valve section which comprises a regulating chamber as well as a seesaw-like operator valve actuated by a suitable electro-magnetic actuator (see, for example, U.S. Pat. No. 4,251,025, column 7, lines 4-7). Through the present invention, substantially simplified controls may be used; for example, no separate regulating chamber and no electro-magnetic actuator is required within the fuel gas controls disclosed in the present application.